Parallel lines

One interesting fact that stands out, and perhaps ironically gives reason to my love of transport history. Railways in the uk, and most of the world, use a track gauge (width between the rails) of 4ft 81/2. This is not some scientifically derived figure giving optimum performance for railways, but a figure derived from roman times. When wagons began to be used for mass transit during the Roman age, a fairly standard size was derived for wheels so that they could follow in the ruts of previous vehicles. The size of this was dictated by the width of the horse, allowing space for the horse to move. This was about 4 81/2, and this gauge remained fairly standard into the 19th century, when little George Stevenson looked out of his bedroom window at the mining trail ways (horse drawn loads on metal rails, the forerunner of the railway). When he developed his first steam hauled locomotive, nothing seemed more natural than to adopt the same width, and the impact is still felt today.